1. Field of the Invention
This invention relates generally to scanning probe microscopes, and more particularly relates to a scanning probe microscope such as an atomic force microscope adapted for use in a specimen chamber of a scanning electron microscope.
2. Description of Related Art
Scanning probe microscopes are useful for imaging objects as small as atoms. Scanning probe microscopy is closely related to scanning tunneling microscopy and the technique of stylus profilometry. However, in a scanning probe microscope, such as an atomic force microscope, a laser beam is typically deflected by a reflective lever arm to which the probe is mounted, indicative of vertical movement of the probe as it follows the contours of a specimen. The deflection of the laser beam is typically monitored by a photodetector in the optical path of the deflected laser beam, and the specimen is mounted on a stage moveable in minute distances in three dimensions. The specimen or probe can be raster scanned while the vertical positioning of the probe relative to the surface of the specimen and the force between the probe and the specimen are maintained substantially constant by a feedback loop with the photodetector controlling the vertical positioning of the specimen.
Scanning probe microscopes, and particularly atomic force microscopes, are useful in examining integrated circuit wafers because the microscope can resolve to atomic dimensions. However, examination of an entire specimen with a scanning probe microscope can be extremely time-consuming and expensive. Scanning electron microscopes can be used more efficiently for scanning an integrated circuit specimen, but they are not capable of imaging the surface of the specimen with the high resolution three-dimensionality of a scanning probe microscope.
Scanning probe microscopes have been utilized in combination with scanning electron microscopes. By positioning the scanning probe microscope within a specimen chamber of a scanning electron microscope, it is possible to generally examine the surface of the specimen with the scanning electron microscope, and to then examine specific areas of interest with higher resolution with the scanning probe microscope. A scanning probe microscope can also be used in different modes, such as to examine electrical and other properties of the specimen. However, there is a need for improved vibration isolation of the scanning probe microscope within the specimen chamber of the scanning electron microscope, because the scanning probe microscope is more sensitive to external vibrations than the scanning electron microscope.
Conventional techniques for utilizing scanning probe microscopes in combination with scanning electron microscopes have also presented the technical difficulty of adjusting positions and interchanging items such as the sample, or the probe and laser of the scanning probe microscopes, and the like, once the scanning probe microscope was sealed within the evacuated scanning electron microscope. The most common and simplest approach-to providing such access involves breaking the vacuum in the scanning electron microscope chamber, and removing the entire scanning probe microscope system, which requires the rather lengthy and tedious process of recreating a full vacuum within the scanning electron microscope chamber once the adjustments to the scanning probe microscope have been made. Another approach to providing access to the scanning probe microscope has involved manipulating the items to be changed or adjusted within the scanning electron microscope vacuum chamber by remote control within the full vacuum in the vacuum chamber, although this is typically not entirely satisfactory due to the difficulty of providing for remote control of every possible contingency. Although scanning probe microscopes have been used within ultra high vacuum chambers equipped with a vacuum interlock, such scanning probe microscopes are commonly permanently mounted in the chamber, while individual elements such as samples and probes are capable of being exchanged through the vacuum interlock. It would be desirable to provide for an apparatus and method of inserting and removing the scanning probe microscope, sample, scanner, and mounting assembly without breaking the vacuum within the scanning electron microscope vacuum chamber.
It would also be desirable to provide a modular scanning probe microscope combination scanner and cantilever probe assembly than can be readily and easily removed and replaced from the scanning probe microscope, to facilitate interchange of such parts with other modular scanning heads, such as a scanning tunnelling microscope head or a scanning thermal head, for example. It would also be desirable to provide an external docking station for the scanning probe microscope of the invention, to allow the scanning probe microscope to also be used independently of the scanning electron microscope. The present invention meets these needs.